Kyle Shatter is an agent with SINTAC.
"Special Intel and Tactics" is the full name of this organization. That agency, according to Special Agent Preston Harvey, a man would become the Director, "is invisible. Unknown by even the lawmakers on the Hill. No one knows we exist. We report directly to the President. Not his assistant. Not his Chief of Staff, and not even the Vice President."
No one applied for a job with SINTAC. Potential candidates, men and women who had no idea the agency existed or that they were being considered for the job, were hired by the Council on International Relations, a prominent think tank. It was while there they would be analyzed and tested and if found to be worthy, told about and offered a job.
Such is the way that Kyle Shatter was introduced to Harvey and SINTAC two and a half decades before the first recorded adventure. [Note of clarification here: that story jumps back and forth in the telling, switching between the life Shatter had before he was employed with the group and the 'present' time.]
SINTAC is the kind of 'deep state' organization that conspiracy theorists warn everyone about and that sane people pooh-poohed as being impossible to pull off. SINTAC has been in existence for well over 100 years working tirelessly to preserve the Constitution by consistently breaking it. It maintains its anonymity by making sure that anyone who threatens it is eliminated, including would-be agents who fail to make the grade or current agents who disobey orders. Or even its titular head, the President, if that leader decides SINTAC is more danger than good, as one did back in 1963.
Shatter is an exceptional agent for SINTAC and has been for, as stated, 25 years, which makes him in his late 40s in those parts of the stories taking place in the current time. He is extremely sharp and quite dedicated to the mission of SINTAC to preserve the country by strenuously removing its enemies.
He is also someone with a unique attribute that has both saved his life on many, many occasions and made him noticed and looked on a bit strangely for all those years he has had it.
Most people are said to have an inner voice that, if they are smart enough to heed it, warns them of danger and points out the true path to take in a dilemma. Since an incident that took place as Shatter was nearing graduation from college and Shatter experience horrible pain in his head and passed out from it, Shatter actually hears, not senses, that special voice.
He talks to it and it talks back. He has learned to do the communicating in private whenever possible or in a whisper if stuck around people, but otherwise the talking is much like he would do with other people. Except there is no arguing or debate. That voice, which Shatter believes is really him putting his subconscious thoughts and analysis into words that only he can hear inside his skull, is extremely sharp and observant and quite quick with its analysis and has saved his life on more occasions than is worth counting.